Computer systems comprising a power supply unit and a system board having expansion connections to connect expansion components are known. A multitude of personal computers (PCs) comprising a power supply unit installed and a system board are known, for example. Typically, components arranged directly on the system board such as a processor, and expansion cards plugged into plug-connectors of the system board are supplied with an operating voltage of the power supply unit via voltage supply lines provided on the system board. Other components such as mass storage drives are supplied with operating energy directly from the power supply unit via a separate cable connection.
FIG. 7 schematically shows an exemplary system configuration of a known computer system 1. Computer system 1 comprises a system board 2, an installed power supply unit 3 as well as three storage drives 4a to 4c. A processor 5, a chip set 6 as well as two expansion connections 7a and 7b in the form of plug connectors that receive expansion cards are provided on the system board. A graphics card 8 is inserted into the first expansion connection 7a. 
The power supply unit 3 converts a line AC voltage, externally provided into one or a multitude of controlled DC voltages that supply the components of the computer system 1. The power supply unit 3 delivers the supply voltages to the individual components via cable connections and corresponding plug connectors. In particular, the power supply unit 3 connects to the drives 4a to 4c via plug connectors 9a to 9c. Furthermore, the power supply unit 3 connects to the system board 2 via two further cable connections and plug connectors 10a and 10b. The operating voltages provided by the plug connectors 10a and 10b are distributed further across the individual components of the system board 2, possibly including components connected to the expansion connections 7a and 7b. To that end, a voltage converter 11 is additionally provided that converts the DC voltages of 5 and 12 V, usually provided by the power supply unit 3 into a suitable voltage to operate the processor 5, for example, 1.5 V.
A particularly high-performant graphics card 8 is accommodated in the expansion connection 7a. The graphics card 8 particularly has power consumption beyond a power limit indicated in a specification of a bus system or of the expansion connection 7a. For example, the expansion connection 7a is a slot according to the PCI Express (PCIe) standard with a maximum power output of 75 Watt per slot and the graphics card 8 is a high-performance graphics card with a power consumption of up to 150 Watt. To provide the additional power required to operate the graphics card 8, the computer system 1 comprises a further cable connection having another plug connector 12 via which the graphics card 8 directly connects to the power supply unit 3.
Three data connections 13a to 13c transfer data and commands between the storage drives 4a to 4c and the system board 2 as well as components arranged thereon such as in particular the chip set 6.
Computer systems such as shown in FIG. 7 allow a modular and flexible system design. However, there is a disadvantage in that the power supply unit 3 needs to be dimensioned such that it is capable of supplying all possible system configurations with a sufficient power. Just as well, the power supply unit 3 needs to comprise cable connections and plug connectors 9, 10 and 12 according to a plurality of standards for a plurality of possible components. This leads to an oversizing of the power supply unit 3 in many system configurations and, thus, to a decrease in energy efficiency. In addition, such a system configuration causes unnecessary costs on the part of the manufacturer.
EP 1 600 844 A2 discloses a method and a device that provides increased power to a storage assembly of a storage subsystem of a computer to increase storage performance and operating stability. In particular, a power greater than the power level available through the main board of the computer is to be provided. The device comprises a supply device that supplies an input voltage to the storage subsystem directly from a power source such as in particular an ATX power supply unit.
DE 696 36 406 T2 discloses a device for voltage control in a computer system comprising a voltage control module. The device is characterized in that the voltage control module is detachable and comprises a plug receptacle assembly containing a multitude of plug receptacles mounted on the detachable voltage control module to transmit control signals and voltages. Furthermore, the device comprises a plug connector that receives the plug receptacle assembly of the detachable control module, wherein the plug connector is coupled to the computer system via a multitude of pins.
It could therefore be helpful to provide alternative design concepts for computer systems and computer systems that preferably allow a high level of modularity and are energy-efficient in operation and cost-efficient in manufacture.